This invention relates to a method for the determination of NO.sub.2 and ozone, to the reactions of NO.sub.2 and ozone with solid alkali metal halides, and the reaction of NO.sub.2 with various salts to produce NO.
In recent years, recognition of environmental limitations has led to widespread qualitative and quantitative studies and analysis of atmospheric pollutants, such as nitrogen dioxide and ozone. Numerous devices and techniques have been proposed over the years for detecting such pollutants. However, most of the prior art techniques and devices have sought to simply detect or make relatively gross measurements of the pollutants. Other prior art devices and techniques have permitted more refined quantitative measurements, but have required extensive time, skilled technicians, and equipment which was often elaborate, delicate, expensive and required considerable readjustment and maintenance. It has been found that the release of halogen permits measurement of pollutants at the parts-per-million level when employed with solid state gaseous halogen sensors, such as those disclosed in U.S. Pat. No. 3,764,269. However, the halogen release and measurement process has not been adapted to the measurement of combined NO.sub.2 and O.sub.3 because of the lack of a suitable reagent to produce halogen in the gaseous state at about ambient temperatures.
Further, it is known that when NO undergoes oxidation by O.sub.3 to NO.sub.2, there is a detectable light emission, the intensity of which is directly proportional to the NO so reacted. This reaction has been suggested as a means for detecting and measuring NO.sub.2 in air by utilizing the thermal conversion of NO.sub.2 to NO followed by re-conversion of NO to NO.sub.2 by ozone and measurement of the light emission associated with the reaction. However, the thermal conversion of NO.sub.2 to NO requires high temperatures in the order of 200.degree. C and higher for completion and also converts NH.sub.3 to NO.